iPhone device vs. iPhone simulator

Question

I have heard of apps not working properly on the simulator but working properly on the actual iPhone device. Has anyone experienced an app that runs perfectly in the simulator but not on the actual iPhone device?

Answer 1

Filenames are case-sensitive on the iPhone, but not in the simulator.

So, for example, if you try to load an image with UIImage *iconImage = [UIImage imageNamed:"MyIcon.png"] , but your resource is actually named "myicon.png", then it will work on the simulator, but not on the device.

Answer 2

If your app is graphics intensive, like say a game, the performance of the simulator DOES NOT resemble at all that of the hardware. Your application will probably be smooth and work great on the simulator, but on hardware it'll likely render at a crawl unless you know what your doing. You can easily go from 60fps to 3fps between Simulator and hardware.

Answer 3

The order in which function/constructor parameters are evaluated is different:

int i = 0;

int f() { return ++i; }

int a, b;

int test(int p1, int p2) {

    a = p1;

    b = p2;

}

test( f(), f() );

//simulator: a = 2, b = 1

//device: a = 1, b = 2

Answer 4

Trigonometry functions may return different results:

float a = cosf( 0.108271248639 );   
printf("%.12f", a);

//simulator: 0.994144439697
//device:    0.994144380093

Answer 5

I know there are some differences in the OpenGL ES implementation between the device and the simulator. From what I understand this is mainly because of the graphics chip on the iPhone (PowerVR MBX) having vastly different capabilities than other mac machines. Many of the hardware limits are not enforced in the simulator, so it is entirely possible to get something running in the simulator that will totally crash on the device.

There are also some OpenGL ES extensions that are supported by the iPhone hardware that are not supported in the simulator. I believe the major one is PowerVR texture compression (PVRTC).

Another problem area can be memory footprint. Anecdotally, I have not seen the simulator automatically enforce the memory limitations of the device. Therefore, it is possible to have something that runs in the simulator fine, happily consuming copious amounts of RAM and never bothering to free any of it only to be swiftly terminated after a short continuance of such behaviour when running on a device.

Answer 6

Fingertips are larger than the 1 pixel endpoint of a mouse cursor. To do proper, even minimal, usability testing you should deploy your App to a device.

Answer 7

There are certain bits of code that won't work on the simulator (using the iPhone Keychain, for example), but for almost all applications, the simulator will work exactly like the iPhone.

That said, there's absolutely no replacement for testing on a real device.

Answer 8

I had a problem running a relatively simple 1/30 sec timer to do updates for a game. It runs fine in the simulator, and freezes out input on the device.

Answer 9

Also note that you will be compiling against the OS X frameworks (where applicable) when building for the simulator so you could be using methods and classes that aren't available on the iPhone versions of the frameworks.

One example I can think of off the top of my head is NSPredicate. I was able to compile and run an app using NSPredicate in the simulator, but it wouldn't compile for the device since that class isn't available.

Answer 10

If you enable GCC_ENABLE_FLOATING_POINT_LIBRARY_CALLS, your app will crash all over the place in the simulator but work on the iPhone.

Quartz graphics calls in the iPhone simulator are faster than Java2D calls on the same computer--wicked fast.

Answer 11

我在内存饥渴的应用程序中遇到了一些问题，模拟器可以正常工作（因为它会假设iPhone / iPod Touch的内存全部都是你玩的），而设备会崩溃（因为其他应用程序泄露了和苹果背景服务占用了一些内存）我没有实现适当的内存管理或对didReceiveMemoryWarning选择器的响应。

Answer 12

One big thing that took me a while to spot was that the simulator does not support device tokens, so any code that involves those will not run on the simulator.

I had a bug where the app would work fine on the simulator, but would crash when I ran it on a device because there was a bug in the device token code. I couldn't figure it out for the longest time!

Answer 13

There are many trivial examples. For example you can allocate far more memory on the simulator than on a real phone. You cannot receive push notification on the simulator if you don't have a retina Mac, the display dot pitch is different.

At a more fundamental level, the simulator is just that, it simulates the iPhone OS X using Mac OS X. This is evidenced by the fact that the filesystem on the simulator may not be case sensitive but on the phone it will be. More subtly, it does not emulate hardware so things like location will not work the same and 3D is going to be very different - especially if you are using Metal.

You should always test on real hardware.

Answer 14

movie file (m4v type) as my exprience is first time playing properly

but at second time it flickers screen of simulator...

whereas in iPhone device it works fime...

Answer 15

If status bar of application is hidden,In case of simulator it still consumes touch event. But in the device it behaves perfectly.

Answer 16

Without considering the performance differences between the two, there used to be some things that the simulator didn't do correctly - ie it would mess up audio in some cases (see this question ). However since the 2.2 SDK this issue has been resolved and the sound seems to be fine in the simulator. That's not to say that there is some other incompatibilities lurking down there! (Just none I've run into)

Answer 17

I had some sound effects that played fine in the simulator, but not on the device. I had to change the format to something that the device would handle.

Answer 18

Yes - it happened to me the other day. I'm new to the iphone, and so had deleted MainWindow.xib thinking it was unused. The app worked perfectly on the simulator - but crashed when installing on the phone.

Another issue we ran into was our three20 dependencies, which were set to ios 3.2 instead of 4.1. Worked perfectly in the simulator, but bombed on the device (since the files were compiled for the wrong arch).

Answer 19

在模拟器中无法访问iphone视频库，但代码在实际设备上工作正常

Answer 20

Regarding sounds, I was having the same problem. The issue was that the sound encodings that the Simulator supports is a different set of sounds than the device. I hope that helps.

Answer 21

I had many problems with libraries and frameworks when moving from the simulator to the device. Not least that they seem to have different architectures!

Answer 22

I have seen the positioning of objects, like toolbars be different on simulator than on the phone. Very annoying.

Answer 23

Yeah....

Apps compiled for 2.x will work fine on 3.0 device, but it will crash on 3.0Simulator

Note: 1. If you compile for 3.0, app will work fine on 3.0 simulator also... 2. a)Compile for 2.x and launch the app in simulator. b)Now change the iPhone Simulator Hardware to "3.0". c)Then launch the app we installed earlier in step a). CRASH !!!!!!!!

Answer 24

When trying to access the UIDevice.currentDevice(), it returns iOS Simulator instead of the actual device you're testing. This sucks, since you can't do certain things on the simulator.

Answer 25

Resource loading in the simulator is MUCH faster than in the device. For example, loading and displaying a sequence of full-screen UIImages (like a rudimentary video) can look very smooth in the simulator, and choppy on a device.

In fact, remember that there is a huge speed difference between different devices. The original iPhone and the iPhone 3G are slower than the iPod touch 2nd Gen, which is also much slower than the iPhone 3GS, and so on.